A supercharger installation is one of the most material modifications you can declare to a car insurer. It increases power output significantly, changes the car’s risk profile, and affects agreed value. Failing to disclose a supercharger or underdeclaring the associated power increase is a common — and costly — mistake. Forced induction systems (superchargers and turbochargers) are consistently flagged by insurers and industry guides as one of the highest-risk, most heavily scrutinised modification categories — exactly the kind of thing that triggers a closer look if you ever make a claim.¹

Why Insurers Care About Superchargers

Insurers assess risk primarily on the probability and cost of a claim. A supercharged car carries higher risk because:

• Higher power output increases accident probability and severity
• Higher performance attracts younger or less experienced drivers (statistically)
• Supercharged cars are more theft-attractive than standard vehicles
• Associated cooling, fuelling, and drivetrain modifications increase total build value

What to Declare When Adding a Supercharger

When declaring a supercharger installation, provide:

• The brand and model of the supercharger kit (Roush, Whipple, Edelbrock, Kenne Bell, etc.)
• The approximate power increase (before/after dyno figures are ideal)
• Associated modifications: intercooler, fuel system upgrades, ECU tune, clutch, drivetrain
• Whether the car retains full road registration and passes emissions testing

How Much Does Supercharger Insurance Add to Premiums?

Insurers don’t publish a fixed percentage for a supercharger add-on — the impact depends on the specific insurer and how the modification is documented. What consistently moves the number:

• The power increase (a mild Roots blower adding 75hp is treated very differently from a 4-rotor Whipple adding 400hp)
• The car type and market value
• The driver’s age and history
• Whether track use is being added simultaneously

Ask your insurer for the exact figure on your specific build rather than budgeting off a generic percentage — the spread between a mild pulley-and-tune setup and a race-level blower kit is too wide for a single number to be useful.

Finding an Insurer for Your Blown Build

Standard comparison sites rarely return valid policies for supercharged cars. Use specialist brokers who understand forced induction builds. Confirm that the quote explicitly covers the supercharger and associated modifications — not just ‘performance modifications’ as a blanket term. Get the cover note in writing before assuming you’re insured.

Agreed Value for Supercharged Cars

A quality supercharger kit and installation is a real cost most owners underestimate when they think about their car’s total insured value — get an itemised quote from your installer rather than assuming a figure, since it varies by kit, engine, and labour rates. Standard market value policies completely ignore this added value. Request an agreed value policy that explicitly includes the supercharger system and associated modifications in the covered value. Provide receipts, photos, and a dyno sheet to support the agreed figure.

Sources

• Howden Insurance — Declaring Modifications to Your Car Insurer

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“name”: “Do I need to tell my insurer about a supercharger?”,
“acceptedAnswer”: {“@type”: “Answer”, “text”: “Yes, immediately. A supercharger is a material modification that must be declared. Adding one without informing your insurer invalidates your current policy and any claims arising from accidents while the undeclared modification is present could be rejected.”}
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“@type”: “Question”,
“name”: “Will a supercharger make my car uninsurable?”,
“acceptedAnswer”: {“@type”: “Answer”, “text”: “No. Supercharged cars are insurable through specialist modified car brokers and insurers. Premiums are typically higher, but any legitimate specialist insurer will consider a properly declared supercharged build. Standard comparison-site policies may refuse, but specialist providers accept them routinely.”}
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“@type”: “Question”,
“name”: “Does my insurer need to know about an intercooler?”,
“acceptedAnswer”: {“@type”: “Answer”, “text”: “Yes. An intercooler is part of the forced induction system and directly affects power output. It must be declared along with the supercharger. The same applies to fuel system upgrades, enlarged injectors, and ECU tunes associated with the installation.”}
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